• 한국분무공학회지
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• 제28권1호
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• pp.43-48
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• 2023

The waste-heat-recovery boiler with water spray (HR-B/WS) applies the heat exchange between the inlet air and exhaust gas with the water spray into the inlet air. The evaporation of water in the inlet air promotes heat recovery from the exhaust gas so that thermal efficiency can be improved by the enhanced condensing effect. The NOx emission can also be reduced by lowering the flame temperature due to the dilution effect of the water. In this study, the validity of this concept is examined by the practical boiler test performed with a 24 kW condensing boiler under the full load condition according to the water injection amount. The theoretical amount of water injection is calculated under the assumption of full evaporation of the sprayed water, which is calculated as 50 g/min. Since the injected water cannot evaporate fully in the actual system, the maximum water spray amount is set as 100 g/min. The results showed that the water injection can increase the thermal efficiency up to 95.59% and reduce NOx and CO emissions simultaneously to 8.9 ppm and 35 ppm at 0% of O₂. Although the heat energy loss increased due to the unevaporated water, the increase in water injection amount caused higher thermal efficiency due to the increased amount of the evaporated water.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4195-4208
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• 2022

In this study, operator habitability was numerically evaluated in the event of a fire at the main control bench board (MCB) in a reference main control room (MCR). It was investigated if evacuation variables including hot gas layer temperature (HGLT), heat flux (HF), and optical density (OD) at 1.8 m from the MCR floor exceed the reference evacuation criteria provided in NUREG/CR-6850. For a fire model validation, the simulation results of the reference MCR were compared with existing experimental results on the same reference MCR. In the simulation, various input parameters were applied to the MCB panel fire scenario: MCR height, peak heat release rate (HRR) of a panel, number of panels where fire propagation occurs, fire propagation time, door open/close conditions, and mechanical ventilation operation. A specialized-average HRR (SAHRR) concept was newly devised to comprehensively investigate how the various input parameters affect the operator's habitability. Peak values of the evacuation variables normalized by evacuation criteria of NUREG/CR-6850 were well-correlated as the power function of the SAHRR for the various input parameters. In addition, the evacuation time map was newly utilized to investigate how the evacuation time for different SAHRR was affected by changing the various input parameters. In the previous studies, it was found that the OD is the most dominant variable to determine the MCR evacuation time. In this study, however, the evacuation time map showed that the HF is the most dominant factor at the condition of without-mechanical ventilation for the MCR with a partially-open false ceiling, but the OD is the most dominant factor for all the other conditions. Therefore, the method using the SAHRR and the evacuation time map was very useful to effectively and comprehensively evaluate the operator habitability for the various input parameters in the event of MCB fires for the reference MCR.

• 한국지반공학회논문집
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• 제25권4호
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• pp.31-38
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• 2009

최근의 압밀시험(표준압밀시험 또는 자중압밀시험)을 대신하여 성형되는 않은(또는 성형이 불가능한 상태의) 연약한 흙의 압밀거동을 연속적으로 빠르고 편리하게 결정할 수 있는 실험방법이 요구된다. 그래서 본 연구에서는 이와 같은 흙의 압밀 거동을 플로우 펌프에서 발생된 침투압을 이용하여 연속적으로 빠르게 획득할 수 있는 급속압밀실험을 제안하였다. 실험 장치는 삼축셀, 플로우 펌프, 변환기, 데이터처리장치 등으로 구성되고, 실험의 과정은 동일 시료에 대해 침투압에 의한 압밀, 하중재하에 의한 압밀, 압밀 후 투수시험 순으로 연속적으로 진행된다. 또한 본 실험법의 검증을 위해 기존의 표준압밀시험으로부터 얻은 결과와 비교 검토도 이루어졌다. 연구 결과 급속압밀실험법이 연약한 흙의 압밀 침하량 산정에 필요한 데이터를 쉽고 빠르게 산정할 수 있는 방법임을 알 수 있었다.

• 한국지반공학회논문집
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• 제24권6호
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• pp.37-44
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• 2008

낮은 응력 상태에서 모래의 인장강도는 포화도 또는 흡입력에 따라 증가하다 최대값이 이른 후 감소한다. 최대인장 강도는 어느 포화도에서든 발생될 수 있다. 선행 연구에서는 이와 같은 습윤 모래의 인장강도를 정확히 표현한 이론이 제시되었다. 본 연구에서 세 가지 종류의 모래(워싱턴 주 시애틀의 검정 Esperance모래, 오스트리일리아 서부 Perth 해변 모래, Ottawa 모래)에 대해 실시된 일축인장실험, 함수특성실험, 직접전단실험 결과를 이용하여 제안된 이론을 검증하였다. 제안된 닫힌 형식의 식으로 표현된 이론은 이들 모래들로부터 얻어진 실험결과와 비교 시 전체 포화도 영역에서 인장강도 변화양상, 인장강도 크기, 최대인장강도, 최대인장강도가 발생할 때의 해당 포화도 등을 잘 예측하는 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.452-459
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• 2023

The core power control is an important issue for the study of dynamic characteristics in China initiative accelerator driven subcritical system (CiADS), which has direct impact on the control strategy and safety analysis process. The CiADS is an experimental facility that is only controlled by the proton beam intensity without considering the control rods in the current engineering design stage. In order to get the optimized operation scheme with the stable and reliable features, the variation of beam intensity using the continuous and periodic control approaches has been adopted, and the change of collimator and the adjusting of duty ratio have been proposed in the power control process. Considering the neutronics and the thermal-hydraulics characteristics in CiADS, the physical model for the core power control has been established by means of the point reactor kinetics method and the lumped parameter method. Moreover, the multi-inputs single-output (MISO) logical structure for the power control process has been constructed using proportional integral derivative (PID) controller, and the meta-heuristic algorithm has been employed to obtain the global optimized parameters for the stable running mode without producing large perturbations. Finally, the verification and validation of the control method have been tested based on the reference scenarios in considering the disturbances of spallation neutron source and inlet temperature respectively, where all the numerical results reveal that the optimization method has satisfactory performance in the CiADS core power control scenarios.

• Structural Engineering and Mechanics
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• 제81권2호
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• pp.205-217
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• 2022

The thermodynamic properties of shaft lining concrete (SLC) are important evidence for the design and construction, and the spatial variability of concrete materials can directly affect the stochastic thermal analysis of the concrete structures. In this work, an array of field experiments of the concrete materials are carried out, and the statistical characteristics of thermophysical parameters of SLC are obtained. The coefficient of variation (COV) and scale of fluctuation (SOF) of uncertain thermophysical parameters are estimated. A three-dimensional (3-D) stochastic thermal model of concrete materials with heat conduction and hydration heat is proposed, and the uncertain thermodynamic properties of SLC are computed by the self-compiled program. Model validation with the experimental and numerical temperatures is also presented. According to the relationship between autocorrelation functions distance (ACD) and SOF for the five theoretical autocorrelation functions (ACFs), the effects of the ACF, COV and ACD of concrete materials on the uncertain thermodynamic properties of SLC are analyzed. The results show that the spatial variability of concrete materials is subsistent. The average temperatures and standard deviation (SD) of inner SLC are the lowest while the outer SLC is the highest. The effects of five 3-D ACFs of concrete materials on uncertain thermodynamic properties of SLC are insignificant. The larger the COV of concrete materials is, the larger the SD of SLC will be. On the contrary, the longer the ACD of concrete materials is, the smaller the SD of SLC will be. The SD of temperature of SLC increases first and then decreases. This study can provide a reliable reference for the thermodynamic properties of SLC considering spatial variability of concrete materials.

• 한국축산식품학회지
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• 제42권2호
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• pp.280-294
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• 2022

This study aimed to evaluate the effectiveness of propolis extract as a natural preservative for livestock products in term of chemical and microbiological characteristics by meta-analysis. The stages carried out in this study were identification, selection, checking suitability, and the resulting selected articles were used in the meta-analysis. The selection results obtained a total of 22 selected journal articles consisting of 9 articles for analysis of the antimicrobial activity of propolis extract and 13 articles for analysis of the chemical and mirobiological characteristics of livestock products. The articles were obtained from electronic databases, namely Science Direct and Google Scholar. The model used in this study is the random-effect model involving two groups, control and experimental. Heterogeneity and effect size values were carried out in this study using Hedge's obtained through openMEE software. Forest plot tests and data validation on publication bias was obtained using Kendall's test throught JASP 0.14.1 software. The results showed that there is a significant relationship between propolis extract with the results of the antimicrobial activity (p<0.05). In addition, the results of the application of propolis extract on the livestock products for the test microbes and the value of thiobarbituric acid reactive substances (TBARs) showed significant results (p<0.05). Conclusion based on the random-effect model on the effectiveness of antimicrobial activity of propolis extract and their apllication as a natural preservative of the chemical and microbiological characteristics of livestock products is valid by Kendall's test (p>0.05). Propolis in this case effectively used as natural preservatives in livestock products.

• Genomics & Informatics
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• 제21권1호
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• pp.8.1-8.19
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• 2023

Cancer of the stomach is the second most frequent cancer-related death worldwide. The survival rate of patients with gastric cancer (GC) remains fragile. There is a requirement to discover biomarkers for prognosis approaches. Helicobacter pylori in the stomach is closely associated with the progression of GC. We identified the genes associated with poor/favorable prognosis in H. pylori-induced GC. Multivariate statistical analysis was applied on the Gene Expression Omnibus (GEO) dataset GSE54397 to identify differentially expressed miRNAs (DEMs) in gastric tissues with H. pylori-induced cancer compared with the H. pylori-positive with non-cancerous tissue. A protein interaction map (PIM) was built and subjected to DEMs targets. The enriched pathways and biological processes within the PIM were identified based on substantial clusters. Thereafter, the most critical genes in the PIM were illustrated, and their prognostic impact in GC was investigated. Considering p-value less than 0.01 and |Log2 fold change| as >1, five microRNAs demonstrated significant changes among the two groups. Gene functional analysis revealed that the ubiquitination system, neddylation pathway, and ciliary process are primarily involved in H. pylori-induced GC. Survival analysis illustrated that the overexpression of DOCK4, GNAS, CTGF, TGF-b1, ESR1, SELE, TIMP3, SMARCE1, and TXNIP was associated with poor prognosis, while increased MRPS5 expression was related to a favorable prognosis in GC patients. DOCK4, GNAS, CTGF, TGF-b1, ESR1, SELE, TIMP3, SMARCE1, TXNIP, and MRPS5 may be considered prognostic biomarkers for H. pylori-induced GC. However, experimental validation is necessary in the future.

• Smart Structures and Systems
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• 제31권3호
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• pp.259-273
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• 2023

Real-time hybrid simulation (RTHS) is an effective experimental technique for structural dynamic assessment. However, time delay causes displacement de-synchronization at the interface between the numerical and physical substructures, negatively affecting the accuracy and stability of RTHS. To this end, the authors have proposed a model-based adaptive control strategy with a Kalman filter (MAC-KF). In the proposed method, the time delay is mainly mitigated by a parameterized feedforward controller, which is designed using the discrete inverse model of the control plant and adjusted using the KF based on the displacement command and measurement. A feedback controller is employed to improve the robustness of the controller. The objective of this study is to further validate the power of dealing with a nonlinear control plant and to investigate the potential challenges of the proposed method through actual experiments. In particular, the effect of the order of the feedforward controller on tracking performance was numerically investigated using a nonlinear control plant; a series of actual RTHS of a frame structure equipped with a magnetorheological damper was performed using the proposed method. The findings reveal significant improvement in tracking accuracy, demonstrating that the proposed method effectively suppresses the time delay in RTHS. In addition, the parameters of the control plant are timely updated, indicating that it is feasible to estimate the control plant parameter by KF. The order of the feedforward controller has a limited effect on the control performance of the MAC-KF method, and the feedback controller is beneficial to promote the accuracy of RTHS.

• 항공우주시스템공학회지
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• 제17권2호
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• pp.94-102
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• 2023

큐브위성용 태양전지판 분리장치는 열선 또는 저항소자의 발열로 나일론선을 절단하여 구조물의 구속을 해제하는 나일론선 절단방식 구속분리장치가 주로 적용되고 있다. 일반적으로 태양전지판 조립체의 발사하중을 고려한 구조해석을 수행하여 구속분리장치의 설계가 이루어지고 있으나, 발사 이후 궤도 열환경에 대한 구속분리장치의 열적 검토 및 분석사례는 전무한 실정이다. 따라서, 본 논문에서는 현재 개발중인 큐브위성 STEP Cube Lab-II에 적용되는 나일론선 절단 기반 구속분리장치의 열적 안정성 평가를 수행하고자 한다. 위성이 POD (Picosatellite Orbital Deployer)에서 사출되고 태양전지판이 전개되기까지의 분리장치 온도 분포를 검토하여 분리장치의 허용온도 범위 내에서 안정적인 구속 분리가 될 수 있도록 분리장치에 대한 궤도 열해석을 수행하였다. 또한, 열해석 결과를 기반으로 열진공시험을 수행하여 분리장치의 설계를 검증하였다.